1. Field of the Invention
The present invention relates to an ultrasonic microscope having a focusing-coupling mechanism.
2. Description of the Related Art
Japanese Patent Publication No. 59-44582 and Janapanese Patent Disclosure No. 58-196453 disclose ultrasonic microscopes in which a sample is two-dimensionally scanned with an ultrasonic beam, and the waves transmitting through, or reflected from, the sample are processed to form an image for the sample.
Also, the Journal of Acoustic Society of America, Vol. 67 (1980),pp. 1,629-37 discloses a cryogenic ultrasonic microscope which can provide a high-resolution ultrasonic image. The cryogenic ultrasonic microscope has an acoustic lens. Cryogenic fluid is filled in the gap between the acoustic lens and a sample. The cryogenic fluid is, for example, liquid nitrogen, liquid argon, or liquid helium, which transmits sound more slowly and absorbs less than water.
These conventional ultrasonic microscopes have a focusing mechanism which moves a sample rod, coarsely and minutely, thereby moving a sample to a desired position. Because of the use of the focusing mechanism, the conventional microscope is disadvantageous in the following respects:
1. Since the sample rod is often detached from, and attached, to, the focusing mechanism to replace a sample by another, the rod must be easily detached from, and attached to, the mechanism. To facilitate the detaching and attaching of the rod, the microscopes need to have a complex mechanism for attaching and detaching the rod.
2. An O-ring is mounted on the upper end of the sample rod, thus providing a vacuum seal for the cryogenic fluid. Consequently, the upper end of the rod is not firmly sutured to the focusing mechanism, and it is difficult to for the focusing mechanism to move the sample to the desired position.